The production of crude oil from reservoirs typically results in significant quantities of non-produced crude oil remaining in the reservoir. After primary oil recovery has been performed, secondary recovery (typically involving water injection), is commonly used to produce trapped oil. Frequently, much oil remains in the reservoir and tertiary recovery operations have been developed to produce the remaining oil. Most tertiary recovery methods for recovering such remaining crude oil include surfactant-polymer enhanced oil recovery floods, such as injecting a combination of surfactants and polymers in brine solutions into the reservoir. Other methods for enhanced oil recovery may include gas injection, chemical injection, ultrasonic stimulation, microbial injection, and thermal recovery. If the oil recovered using enhanced oil recovery floods cannot be efficiently treated (e.g., the emulsion broken into dry oil and clean water), then most if not all oil producers will be reluctant to conduct chemical floods in favor of other less aggressive and lower recovery processes.
Results of such conventional methods include a produced emulsion that typically contains crude oil, water, surfactant, and polymer. Drawbacks include difficulties in separating the emulsion into clean water and dry oil for efficient recovery of the crude oil and proper disposal of the water in an environmentally safe manner. Heat has been used to aid in resolving such emulsions but is not economical due to the large amounts of water involved. Solvent extraction is disclosed in U.S. Pat. No. 4,559,148, “Method of Extracting and Reutilizing Surfactants from Emulsions,” but is also not practical due to the large capital investment and flammable solvent handling issues.
Consequently, there is a need for improved methods of resolving crude oil and water emulsions. Additional needs include improved methods for demulsifying the produced emulsion to produce a clean separation of the crude oil and water.